The present invention relates to a printer and cartridge assembly and particularly relates to improved apparatus and methods for constructing and operating a high-speed printer and an improved printer ribbon cartridge.
High-speed printers are, of course, well known. Due to evolving customer needs, it has become desirable in many instances to increase the paper handling capability of printers, while simultaneously affording flexibility in handling the paper. For example, it has become desirable to provide multiple paper paths for feeding different types of paper into the printer for different purposes, without the necessity of manually removing one type of paper from the printer in order to feed a different type of paper. More particularly, in a prior printer sold by assignee of the present application, there was provided a single rear paper path including a tractor assembly for the paper, together with an option for a bottom paper feed path. However, the bottom feed path constituted only a roller path and not a tractor-driven paper path. In many situations, tractor feed is more desirable than a friction-driven roller feed because of the precise nature of the feed and the current increasing use of continuous form computer paper. Consequently, it has been found desirable to provide at least two tractor feed paper paths for a printer for feeding paper to the printhead along different paths, i.e., from the front or bottom of the printer along a first path or from the rear of the printer along a second path. It is also desirable to use the same tractor set along each of the two paths or provide two tractor sets for use in the respective paper paths depending on customer needs. Where two tractor sets are employed, the capability of parking the paper in each feed path while feeding paper along the other feed path has also been found desirable. Additionally, and for added flexibility, the printer should have the capability of handling cut-sheet paper manually fed to the printer as well as cut-sheet paper automatically fed to the printer.
Further, many prior printers have various constructional features which substantially increase the cost of manufacture, not only in terms of the cost of the parts necessary to fabricate the printer, but also in terms of the labor necessary to adjust the printer for its designed operations, once assembled. For example, the roller drives on the printer shafts are conventionally formed of a rather expensive material and there has been a need to reduce the expense of those rollers without sacrificing performance. Additionally, printer mainframes have previously been built up from a substantial number of parts, certain of which require adjustment if the printer head in association with the striker bar is to print correctly. Lack of proper initial adjustment, and parts coming out of adjustment with use, have been continuing problems.
Various improvements in the design of the ribbon cartridge itself are possible to reduce the costs of the manufacture of the cartridge, as well as to enhance the performance of the printer. For example, not infrequently the mobius loop of the printer cartridge is ineffective to invert the printer ribbon. The ribbon then extends between the exit and entrance arms of the cartridge in a twisted state, resulting in defective printing. Additionally, mishandling of the cartridge prior to installation in the printer has been a problem. This sometimes results in the printer ribbon being jammed and prevented from being advanced.
The present invention therefore provides novel and improved apparatus and methods for enhancing the performance and capability of a high-speed printer in terms of both the apparatus and methods for printing, as well as effectively reducing the cost of manufacturing the printer. In this connection, it will be appreciated that there are a host of individually improved features in the printer and cartridge hereof which collectively give rise to substantial overall improvements in printer operation and that of its cartridge and that, additionally, there are many novel features which are each notable in their own right as well as when taken in various combinations and permutations.
Therefore, in one aspect of the present invention, there is provided a printer having a printer paper feed path system which enables continuous feed of paper along two paper paths. The paper in each path can be parked so that the paper in the other path can be fed to the printhead for printing. Each paper path may be provided with a tractor set so that continuous forms may be advanced along the selected paper path for printing. Through a novel mounting of the tractor set associated therewith, continuous feed of paper into the print position from either one side, preferably the front, or from the bottom of the printer, is provided along a first paper path. The other, or second, paper path may be located to receive paper through an opening in another side, preferably the rear of the printer, for feeding paper continuously to the print position. Additionally, a third paper path is provided for either manually or automatically feeding cut-sheet paper to the print position. For manual feed, the paper in the first and second paper feed paths is parked in the associated tractor set. For automatic feed of cut-sheet paper, the paper in the second path must be removed, although the paper in the first path must be parked if installed in its associated tractor set.
For certain customer uses, only one tractor set for the continuous feed of paper is employed. Such tractor set is interchangeable between positions for feeding paper continuously along the first and second respective paper paths. For example, when the tractor set is employed for feeding paper along the first paper path, the tractor set may be disposed in alternate positions to feed paper continuously from paper inlet openings disposed in the front or bottom of the printer. Should it be desirable to continuously feed paper from the rear of the printer, the one tractor set may be removed from the first paper path and disposed in the second paper path, whereby paper may be continuously fed from the rear paper inlet opening to the printhead.
There is also provided in accordance with the present invention a novel arrangement of a drive mechanism for purposes of driving the tractor set in any one of its three positions described previously. For example, a drive motor mounted to one side of the printer housing and through a continuously driven belt provides power to a pair of clutch assemblies. When the tractor set is disposed to supply paper along the first path, the clutch assembly associated therewith is actuated such that the belt drive assembly is connected to a drive gear, in turn connected to a tractor set drive gear for advancing the paper. As detailed hereinafter, that tractor drive gear is operable to advance the paper in the tractor set in both of its feed positions for feeding paper through the front or bottom paper inlet openings along the first paper path. When the tractor set is removed from the first paper path and disposed in the second paper path, selection of the second or rear paper feed path from the control panel actuates the second clutch assembly to enable the belt drive to couple another set of drive gears to the printer motor, whereby the tractor set, in the second path, may be continuously driven.
Where two tractor sets are used, a continuous form may be installed in the first tractor set disposed in the bottom or front position to feed paper along the first paper path and an additional continuous form may be installed in the second tractor set disposed in the rear position to feed paper along the second paper path. These forms need not be the same width, length, thickness, weight, etc. When one paper path is selected from the control panel, the other path remains in a paper parked position. That is, the continuous form in the tractor set disposed in the non-selected paper path remains in that tractor set, with its leading edge spaced from the printer drive roller and printhead. This enables the paper in the other tractor set to be fed to the printhead.
More particularly, a load switch on the control panel is pushed to move the paper along the selected paper path to the print position. Other normal print commands follow. When the operator wishes to park this form and use the form parked in the other paper path, the paper may be cut using a method such as a form feed function followed by a tear-off function selected at the control panel. In that method, the paper in the currently selected paper path is then moved to a convenient position to tear the paper off against a tear surface, at which time the paper may be returned by the operator or timed to move back into its normal printing position. The park/path command is then selected and this retracts the paper in the currently selected paper path such that its leading edge is disposed in its tractor set. The park/path control switch is then actuated until the other newly selected paper path is identified on the control panel. Upon the next paper movement command, the clutch solenoid for the previously selected path is deactivated and the solenoid for the clutch assembly of the newly selected path is actuated. This enables the tractor set in the selected paper path to advance the paper therein to the print position where normal print commands may follow for printing on the selected paper. All of the above control panel commands can also be obtained remotely from a data source using escape codes.
It will be appreciated that, with one tractor set disposed along either of the first and second paper feed paths, or with two tractor sets disposed in the first and second paper feed paths, respectively, both first and second paper feed paths can be deselected and cut-sheet paper may be manually fed along a third path. Thus, the continuous paper form in the one tractor set or both continuous paper forms in the two tractor sets may be parked when the manual paper feed path switch is selected on the control panel. This selection deactivates the clutch assemblies. Cut sheets are then loaded through a guide slot at the top of the printer for manual feed into the nip of the main drive roller and nip rollers. When the load switch is pressed, the sheet will load and printing may commence.
Alternatively, an automatic sheet feeder may be provided. When using an automatic sheet feeder, the tractor set for the second paper path is removed. If a tractor set is located in the bottom or front feed position along the first paper path, the paper in that feed position may be parked. By appropriate selection of controls, the automatic sheet feeder then feeds individual cut sheets into the printer assembly.
Another important feature of the present invention resides in the specific construction of the tractor sets, which are interchangeable for use in each of the first and second paper feed paths. Each tractor set includes a support shaft and a drive shaft disposed between opposite end plates. Conventional tractor drive pin assemblies are carried by the tractor set at locations between the end plates such that the pins may engage the paper feed holes to advance the paper. The end plates carry hooks on one end thereof which engage a tractor support shaft carried by the printer. Adjacent its opposite end, each end plate carries a detent for retaining the tractor set in proper position in the selected paper path. A tractor drive gear is carried by the tractor set at each of its opposite ends and is cooperable with a printer drive gear for advancing paper along the tractor set and, hence, the paper path in part defined by that tractor set. The tractor drive gear is substantially encapsulated or covered by a cap, which forms a part of a tractor set detent. A portion of the tractor drive gear is exposed inwardly of the printer for engagement with the printer drive gear in each of the tractor set feed positions. The detent includes a bulbous end and a recess on that end of the cap. A fixed pin and an axially biased pin are mounted in the printer main frame on respective opposite sides of the paper feed paths in each of the three tractor set feed positions. When the hooks of the tractor set are engaged over the tractor support shaft, the caps are retained by detenting engagement with the pins associated with the selected path. The axially biased pin thus enables the tractor set to pivot into its retained position. The caps also serve as protection for printer operators so that articles of clothing or fingers may not be caught up in the gearing interconnecting the tractor set and printer drive assemblies.
Another feature of the present invention resides in the accurate and stable alignment and adjustment of the printhead. Any instability of the printhead causes the print quality to be inconsistent. A principal source of inconsistent print quality is the radial play in the printhead support shaft and associated bearings in the printer frame. The present invention provides a bearing design which eliminates radial play in the printhead support shaft or other shafts used in the printer without substantial increase in cost. According to this aspect of the present invention, a generally circular bearing is provided with an eccentrically mounted bore, for example, a D-shaped bore. A pair of circumferentially extending springs are located along the outside diameter of the bearing for bearing contact within the housing bore. This eliminates radial play between the bearing and the housing bore. A third cantilevered spring is located within the bearing bore flats. This spring forces the shaft to a contact area within the bearing bore which eliminates radial play between the bearing bore and the shaft. The bearing material preferably is an electrically conductive polycarbonate for static discharge, although any suitable thermoplastic bearing material may be used if static discharge is unimportant.
Another aspect of the present invention resides in a unique roller design for the roller shafts. Previously, solid high-density microcellular urethane rollers have been supplied on a shaft in opposition to low-density microcellular urethane rollers. These individual rollers are conventionally bonded into place and ground to size. In accordance with the present invention, a new roller design eliminates the bonding and grinding operations, uses a single common material, and substantially reduces the costs of the rollers. To accomplish this, the basic roller includes an interior hub defining a bore, an outer rim spaced radially from the hub and a series of generally circumferentially extending cantilevered spokes extending from the hub to the bore in the annular space therebetween. The cantilevered spokes deflect under radial pressure to allow various thicknesses of paper to be driven between mating rollers. The deflection of the spokes causes a spring-back effect, which assists to drive the paper forms. The spokes also allow the rollers to conform to irregular shapes or out of roundness in the mating shaft. Preferably, the bore is smaller in diameter than the shaft and enables an interference fit between the shaft and the roller yet still resists radial slippage during paper drive operations. The material is preferably a thermoplastic rubber (polyolefin) having a coefficient of friction of 1.05 against paper forms.
Another novel and unique aspect of the present invention relates to the zero adjustment striker bar. It will be appreciated by those skilled in this art that accurate positioning of the striker bar in relation to the carriage rails and printhead of a printer is absolutely essential. Previously, positioning has been achieved by secondary operations and various assembly adjustments, all of which can readily come out of adjustment. Printers of this type use a rigid striker bar whose position must be adjusted relative to the carriage rail system for distance and/or perpendicularity. Assembly-line adjustments of this type are both time-consuming and expensive. Existing adjustment systems include adjustable cam surfaces against which the striker bar face is loaded, eccentric cams located in the end of the striker bars which are adjusted after assembly, and snugging-down screws. Often the striker bar is tapped into position with a mallet prior to final securement. Other methods previously employed include using a round striker bar which does not rotate during printer operation but is cammed into position by eccentrics. While a printer frame can be machined to a high degree of accuracy, thus eliminating adjustments, this is a highly expensive operation.
In accordance with the present invention there is provided a one-piece printer mainframe molded of a material and by a process which produces the necessary dimensions to eliminate the striker bar adjustment while maintaining print quality. The mold construction is an important aspect of meeting the necessary dimensional characteristics required to eliminate a striker bar position adjustment. Thus, the present main frame is formed from a mold constructed such that the carriage rail holes and striker bar mounting surface are formed by the same piece of the mold at each end. The left striker bar mounting surface and left carriage rail holes are formed by the left side core of the mold. Similarly, the right striker bar mounting surface and right carriage rail mounting holes are formed by the right side core of the mold. The features that form the left and right striker bar mounting surfaces telescope into and are shut off by the main core of the mold. This minimizes positional and perpendicularity error and variance on each end of the system. Thus, no adjustments of the striker bar and rail or the main drive roller are necessary in accordance with this invention. Additionally, the frame enables the belt tension to be spring adjusted and the cable tension to be self-adjusting.
The material chosen for the mainframe is a fiberglass-reinforced thermoset polyester bulk molding compound which is highly dimensionally stable and considered a "zero shrink" material in relation to mold shrink. Mold shrink is listed in the range of 0 to 0.0005 inch per inch, which is extremely low. Typical ranges for similar percentage reinforcement for amorphous thermoplastics are 0.0010-0.0025 inch per inch. This also helps minimize positional variance. The mold process is injection molding.
In another aspect of the present invention, there is provided a printer ribbon cartridge assembly having various unique features. Not infrequently, it has been found that the conventional mobius loops, for example, as set forth in U.S. Pat. Nos. 4,630,948 and 3,989,132, may sometimes be ineffective to invert the ribbon, resulting in poor quality printing and defects. Part of the problem is caused by insufficient tension on the ribbon between the ribbon storage area and the mobius loop. In accordance with the present invention, there is provided a ribbon tensioner to increase the tension of the ribbon before it enters the mobius loop. This straightens the ribbon and increases the reliability of the ribbon tracking through the mobius loop. The ribbon is tensioned by pulling it about two posts which are disposed perpendicular to the direction of ribbon travel.
Another feature of the ribbon cartridge hereof is the ratchet clutch in the ribbon advance knob. Ribbon failure is not infrequently caused by mishandling of the ribbon cartridge prior to its installation in the printer. For example, an operator may rotate the ribbon advance knob in the wrong direction, hence, fouling the ribbon within the cartridge and causing a ribbon failure. In accordance with the present invention, a clutch mechanism is provided between the advance knob and the pinion drive for the ribbon. Consequently, the ribbon advance knob, when turned in the incorrect direction before installing the cartridge in the printer, does not advance the ribbon. The ribbon can be advanced only when the ribbon advance knob is rotated in the proper direction and the pinion driven through the clutch between the advance knob and the pinion. Another feature of the cartridge of the present invention resides in the fabrication of the upper and lower covers of the cartridge. One of the covers is provided, at spaced longitudinal positions therealong, with a series of elongated recesses and one circular recess. The opposite cover is provided with a series of generally circular pins. The pins are received in the recesses with the one pin in the circular recess to accurately locate the covers relative to one another. As a consequence, the tolerances when joining the covers one to the other are tight in the transverse direction but loose in the longitudinal direction.
Accordingly, it is a primary object of the present invention to provide novel and improved high-speed printer apparatus, including various constructional features, methods of operating the printer, and printer ribbon cartridges for the printer.
In a preferred embodiment according to the present invention, there is provided a printer, comprising a printer frame and a printhead carried by the frame for printing on paper. Means carried by the frame define first and second discrete paper paths for supplying paper to the printhead. Means are provided for continuously feeding paper along each of the respective paper paths to locate the paper fed along one or the other of the paths in position relative to the printhead for printing, including at least one tractor set for engaging and feeding the paper and means for releasably mounting the tractor set in the frame for movement between first and second positions for feeding paper along the first and second paper paths, respectively. Means are also carried by the frame for driving the tractor set when located in position for feeding paper along the first and second paper paths. Also provided are means for selectively actuating the feed means for feeding paper along one of the feed paths including means carried by the frame for driving the tractor set when located in a corresponding position for feeding paper along the one paper path.
In another preferred embodiment according to the present invention, there is provided a printer, comprising a printer frame and a printhead carried by the frame for printing on paper. Means carried by the frame define first, second and third discrete paper paths for supplying paper to the printhead, together with means for continuously feeding paper along the first and second paper paths to locate the paper fed along the first and second paths into position relative to the printhead for printing. The third discrete paper path includes means for feeding cut-sheet paper along the third path into position relative to the printhead for printing. Means are also provided for selectively actuating the feed means for feeding paper along one of the first, second and third feed paths into position relative to the printhead for printing.
In still another preferred embodiment according to the present invention, there is provided a printer, comprising a printer frame and a printhead carried by the frame for printing on paper. Means carried by said frame define first and second discrete paper paths for supplying paper to the printhead, together with means for continuously feeding paper along each of the respective paper paths to locate the paper fed along one or the other of the paths in position relative to the printhead for printing including first and second tractor sets for engaging and feeding the paper along the first and second paths, respectively. Also provided are means carried by said frame for driving the tractor sets and means for selectively actuating the feed means and driving one of the tractor sets for feeding paper along a corresponding one of the feed paths.
In a further preferred embodiment according to the present invention, there is provided a method of operating a printer having a frame, a printhead and a tractor set for advancing paper toward the printhead for printing, comprising the steps of providing first and second discrete paper paths for supplying paper to the printhead, locating the tractor set in a first position along one of the first and second paper paths for advancing the paper along the one path toward the printhead, driving the tractor set when in the first position, to advance the paper along the one path toward the printhead, removing the tractor set from the first position along the one paper path, locating the tractor set in a second position along the other of the first and second paper paths for advancing the paper along the other path toward the printhead, and driving the tractor set when located in the second position to advance the paper along the other path toward the printhead.
In a still further preferred embodiment according to the present invention, there is provided a method of operating a printer having a frame, a printhead and a tractor set for advancing paper toward the printhead comprising the steps of providing first, second and third discrete paper paths for supplying paper to the printhead, providing feed means for feeding continuous paper along the first and second paper paths to locate the paper fed along the first and second paths into position relative to the printhead for printing, providing feed means for feeding cut-sheet paper along the third path into position relative to the printhead for printing, and selectively actuating the feed means for feeding paper along one of the feed paths into position relative to the printhead for printing.
In a still further preferred embodiment according to the present invention, there is provided a method of operating a printer having a frame and a printhead comprising the steps of providing first and second discrete paper paths in the frame for supplying paper to the printhead, providing first and second tractor sets for engaging and feeding the paper along the first and second paths, respectively, providing drive means for each of the tractor sets and selectively actuating the drive means for actuating one of the tractor sets for feeding paper along a corresponding one of the feed paths.
In an even further preferred embodiment according to the present invention, there is provided a tractor set for feeding paper in a printer having a drive gear for driving the tractor set, comprising a pair of mounting members adjacent opposite ends of the tractor set, means for connecting the mounting members one to the other, means carried by the connecting means for advancing paper along the tractor set between the mounting members, including a pair of tractors each including a plurality of drive pins for engaging the paper, and means carried by the mounting members releasably connecting the tractor set to the printer. Means are also provided for driving the paper advancing means, including a gear carried by the tractor set adjacent one end thereof, and an enclosure for the gear carried by the tractor set, the enclosure being configured to extend about substantially a major portion of the exposed portions of the gear teeth of the tractor set drive gear, leaving a portion of the gear teeth exposed for meshing engagement with the printer drive gear whereby users of the tractor set are substantially protected from the meshing engagement of the gears.
In a still further preferred embodiment according to the present invention, there is provided a tractor set for feeding paper in a printer having a drive gear for driving the tractor set, comprising a pair of mounting members adjacent opposite ends of the tractor set, means for connecting the mounting members one to the other, and means carried by the connecting means for advancing paper along the tractor set between said mounting members including a pair of tractors each including a plurality of drive pins for engaging the paper. Means are carried by the mounting members for releasably connecting the tractor set to the printer including means at opposite ends of the tractor set in part defining detents. Also provided are means for driving the paper advancing means, including a gear carried by the tractor set adjacent one end thereof.
In a still further preferred embodiment according to the present invention, there is provided a printer comprising a printer frame and a printhead carried by the frame for printing on paper, and means carried by the housing to define alternate paper paths for feeding paper to a position enabling the printhead to print on the paper, including a tractor set for engaging and advancing paper along the paths toward the print position. Means are provided for mounting the tractor set for movement between positions for feeding paper along the alternate paper paths and for driving the tractor set in each of the tractor set positions.
In a still further preferred embodiment according to the present invention, there is provided a printer comprising a printer frame, a printhead carried by the frame for printing on paper, means carried by the frame for defining first and second paper paths for feeding paper to a position enabling the printhead to print on the paper, including a tractor set for engaging and advancing paper along the paths, means for releasably mounting the tractor set in the frame for movement thereof between positions for feeding paper along the first and second paper paths, respectively, and means for driving the tractor set in each of the positions.
In a still further preferred embodiment according to the present invention, there is provided a paper handling apparatus for a printer comprising a roller formed of an elastic material and having a hub, a rim radially spaced from the hub and a plurality of spokes circumferentially spaced one from the other about the roller and extending between the hub and the rim, each spoke being joined at its ends to the hub and the rim, respectively, at circumferentially different locations about the roller whereby at least one of the spokes exerts a generally radially outwardly directed force against the rim upon inward deflection of a portion of the rim adjacent the one spoke.
In a still further preferred embodiment according to the present invention, there is provided a printer mainframe comprising end plates and a platform spanning between the end plates, the platform and the end plates being integrally molded one with the other, the end plates having printer carriage rail holes and striker bar mounting surfaces dimensioned to eliminate striker bar position adjustments.
In a still further preferred embodiment according to the present invention, there is provided a ribbon cartridge for a printer comprising a housing including an elongated body having ribbon exit and entrance arms adjacent opposite ends and spaced one from the other, with a ribbon disposed in said housing and extending between the entrance and exit arms. Means carried by the housing are provided for pulling the ribbon in one direction from the housing through the exit arm to the entrance arm and into the housing, with manually operable means coupled to the pulling means for rotation in one rotary direction to pull the ribbon in one direction. One-way clutch means interconnect the manually operable means and the pulling means for preventing movement of the ribbon in the opposite direction upon rotation of the manual means in the opposite rotary direction.
In a still further preferred embodiment according to the present invention, there is provided a ribbon cartridge for a printer comprising a housing including an elongated body having ribbon exit and entrance arms adjacent opposite ends of the body and projecting to one side thereof, with a ribbon disposed in the housing and extending between the exit and entrance arms. Drive means are provided in the housing for pulling the ribbon from the housing through the exit arm and into the entrance arm. The housing includes upper and lower covers substantially coextensive with the housing, one of the covers including means defining a plurality of slots spaced one from the other along the edge of one cover, the other of the covers including a plurality of pins extending therefrom for reception in the slots, the slots being elongated in the direction of elongation of the body a distance greater than their width whereby, upon reception of the pins in the slots in an interference fit, the registering slots and pins provide tight tolerances in the transverse direction and loose tolerances in the longitudinal direction. Preferably, one of the covers includes a circular recess for receiving a pin of the other cover whereby the covers are accurately located relative to one another by such single pin engaging in the circular recess.
In a still further preferred embodiment according to the present invention, there is provided a bearing for mounting a shaft, comprising a bearing having an outer cylindrical surface defining a first axis and an internal bore having a generally cylindrical inner surface and defining a second axis radially offset from the first axis. Means are provided carried by the body for mounting a shaft against rotation relative to the body. A pair of cantilevered springs are spaced one from the other about the outer surface, each spring having a proximate end secured to the body, a distal end free of the body and an intermediate portion between the proximate and distal ends substantially conforming to the cylindrical outer surface, the pair of springs being adapted to engage the walls of a bore to force the bearing to a contact area within the bore. An axially extending cantilevered leaf spring extends along the internal surface in an axial direction with proximate and distal ends axially spaced one from the other to eliminate radial play between the bearing bore and the shaft.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.